Magnetic hard disk drives store and retrieve data in computers and other consumer electronics devices. A magnetic hard disk drive includes one or more heads that can write and read information on a corresponding magnetic surface of a spinning disk. For convenience, all heads that can write are referred to as “write heads” or “heads” herein, regardless of other devices and functions the write head may also perform (e.g. reading, micro-actuation, flying height control, touch down detection, lapping control, localized disk media heating, etc). Each write head is a sub-component of a head gimbal assembly (HGA). The HGA also includes a suspension assembly for holding the head and providing a plurality of electrical connections thereto. The suspension assembly typically includes a fragile laminated flexure to carry the electrical signals to and from the head.
The head typically comprises a slider that includes an air bearing surface (ABS) that faces the magnetic disk surface, a trailing face, and a mounting face that is opposite the ABS and that faces away from the ABS. A magnetic sensor and a plurality of head bond pads are typically disposed on the trailing face of the slider. The mounting face of the slider is typically permanently bonded to a tongue portion of the fragile laminated flexure by an adhesive, in a position such that the plurality of head bond pads are aligned with corresponding bond pads on the laminated flexure.
Conventionally, the head writes tiny magnetic transitions on the magnetic disk surface by applying sufficient magnetic field to the desired microscopic disk surface location to overcome the coercivity of the disk surface material there, and thereby change the remnant field there. However, market demand for disk drives having ever higher data storage capacity has motivated investigation into the possible use of “energy assisted” magnetic recording (EAMR), in which writing is accomplished not only by local application of a magnetic field, but also by local application of laser light for localized heating of the disk surface. EAMR may enable the writing of smaller transitions, and thereby increase the areal density of data stored on the disk surface. Most proposed EAMR technologies require the addition of a laser light source on a slider of the write head, for example bonded to the back face of the slider. EAMR is sometimes also referred to as HAMR (“heat assisted magnetic recording”).
Driving the laser light source for EAMR requires electrically conductive paths or traces in the laminated flexure that connects to the write head. Conventionally, the conductive traces used to drive the laser device are additional to the other conductive traces that carry the write signal to the write head. However, space available on the flexure for additional conductive traces is limited. Moreover, the additional electrical connections required for additional conductive flexure traces increases the time to manufacture HGAs and head stacks, manufacturing scrap, and manufacturing costs, and can reduce manufacturing yield. Accordingly, there is a need in the art for improved structures and methods to drive laser devices in EAMR disk drive applications with more efficient use of space available on the laminated flexure.
Furthermore, in EAMR disk drives, and at present and future high data rates, the skew (i.e. the time lead or lag between transitions in the write signal and transitions in the signal that drives the laser device) can be undesirably frequency dependent. Yet it is important that these signals be synchronized so that the heat produced by the laser will assist the writing of magnetic transitions on the disk. Accordingly, there is a need in the art for improved structures and methods to reduce the frequency dependence of skew when driving laser devices in EAMR disk drive applications.